Hook's escapement was like.
[Illustration: Fig. 158]
[Illustration: Fig. 159]
On looking at Fig. 156 we see the escape wheel _R_, which was flat and
in the form of a ratchet; it was provided with two balances. _B B_
engaging each other in teeth, each one carrying a pallet _P P'_ upon its
axis; the axes of the three wheels being parallel. Now, in our drawing,
the tooth _a_ of the escape wheel exerts its lift upon the pallet _P'_;
when this tooth escapes the tooth _b_ will fall upon the pallet _P'_ on
the opposite side, a recoil will be produced upon the action of the two
united balances, then the tooth _b_ will give its impulse in the
contrary direction. Considerable analogy exists between this form of
escapement and that shown in Fig. 153 and intended for clocks. This was
the busy era in the watchmaker's line. All the great heads were
pondering upon the subject and everyone was on the _qui vive_ for the
newest thing in the art.
In 1674 Huygens brought out the first watch having a regulating spring
in the form of a spiral; the merit of this invention was disputed by the
English savant, Dr.
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